Variable flow oil pumps may provide engine oil at a pressure optimized for efficient engine operation, improving fuel efficiency. Additionally, the use of piston-cooling jets may provide enhanced piston cooling at high engine speeds and loads, allowing engine operation at these operating points. However, with the inclusion of variable flow oil pumps and/or piston-cooling jets, new and additional components in the lubrication system are provided. These new components may not be currently accounted for in current methods to detect and/or diagnose component degradation.
One approach for diagnosing degradation of piston-cooling jets is disclosed in U.S. Patent Application No. 2011/0224883. Here, a method for diagnosing degradation of a piston-cooling jet valve to open may be determined based on variation in engine oil pressure due to a commanded switch of the valve. However, this method relies on particular operation of a controllable valve. Further, the degradation detection may provide erroneous results due to the changing oil pressure provided by a variable flow oil pump, due to oil pressure fluctuations in addition to those caused by the commanded valve switch.
The inventors have recognized the issues with the above approach and offer a method to at least partly address them. In one embodiment, an engine method comprises indicating degradation of a piston-cooling jet system in response to a relationship between engine speed and oil pressure at maximum oil pump displacement conditions.
In this way, identification of degradation of a piston-cooling jet system may be determined. In one example, the relationship may be used to determine the spring preload set point of a check valve of the piston-cooling jet, and if the set point is outside an expected range, engine control strategies may be adapted to account for the change. Further, if degradation is indicated, an operator may be notified, and engine operating parameters may be adjusted in order to reduce engine issues due to the degraded piston-cooling jets.
The present disclosure may offer several advantages. For example, engine lubrication efficiency may be increased by determining the functioning of various lubrication components. By increasing engine efficiency, fuel economy may be improved. Furthermore, by detecting worn or low-functioning components, an operator of the vehicle may be notified and/or engine control strategies may be adjusted to compensate for the worn components, reducing the likelihood engine components will suffer degradation resulting from operation with undesired engine oil pressure.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.